Spatial Taming and Trapping of Molecules

达德利·赫施巴赫 (Dudley Herschbach) 在实验物理化学计划的支持下开发了一种用于操纵和捕获具有极低平移能的分子的装置。 这将通过对从高速对转转子外围排出的气体进行分子束膨胀冷却来实现，使得转子尖端运动抵消膨胀速度。 还可以选择通过共同旋转转子来将速度提高到高于热速度。 基本可行性是使用 Xe 建立的，该技术正在开发中并扩展到其他气体（O2、Cl2、HCl 和 CO）。 正在进行的五项开发是：1）改进转子结构并消除设计缺陷； 2）增加超音速膨胀的压力，以达到较低的温度； 3）提高真空度以减少慢速分子散射； 4) 开发收集慢分子的技术，5) 使用脉冲气体喷嘴改善超音速束的单向性。 与这些发展同时进行的还有 a) 低温化学研究，特别是 OH 的化学研究，b) 使用不均匀的静态场和激光场来散射或聚焦慢粒子，以及 c) 通过分子衍射演示慢粒子的德布罗意性质。这些研究正在开发一种装置，其中分子可以冷却到非常低的温度，低至比绝对零温度高 1 度。 在这些温度下，分子的速度为每秒几十米，并且其波长与其尺寸相比很大。 这完全改变了分子之间反应碰撞的性质，开辟了化学行为的新领域。 该装置可以连续增加分子的速度，从而能够确定能量对过程的影响，并观察到传统行为的转变。

Dudley Herschbach is supported by the Experimental Physical Chemistry Program to develop an apparatus for manipulating and trapping molecules with very low translational energies. This will be accomplished by molecular beam expansion cooling of gases exiting from the periphery of a high speed contra-rotating rotor such that the rotortip motion cancels out the expansion velocity. There is also the option of increasing the velocity above thermal by co-rotating the rotor. The basic viability was established using Xe and the technique is being developed and extends to other gases (O2, Cl2, HCl and CO). Five developments being made are to: 1) improve the rotor construction and eliminate design weaknesses; 2) increase the pressure for the supersonic expansion to achieve lower temperatures; 3) improve the vacuum to reduce slow molecule scattering; 4) develop techniques for collecting the slow molecules and 5) use a pulsed gas nozzle to improve the uni-directional nature of the supersonic beam. In parallel with these developments, there are a) studies of chemistry at low temperatures, specifically that of OH, b) use of inhomogeneous static and laser fields to scatter or focus the slow particles and c) demonstrations of the de Broglie nature of the slow particles by molecular diffraction.The studies are developing a device in which molecules can be cooled down to very low temperatures, as low as one degree above absolute zero of temperature. At these temperatures, the molecules have speeds of a few tens of meters per second and have wavelengths large compared with their size. This entirely changes the nature of the reactive collisions between molecules, opening up a new realm of chemical behavior. The device is such that the speed of the molecules can be increased continuously, enabling the effect of energy on the process to be determined and the change-over to conventional behavior to be observed.